Collets and other workholders



Dec. 13, 1960 c. J. LINZELL 2,964,325

COLLETS I AND OTHER WORKHOLDERS Filed Jan. 11, 1960 2 Sheets-Sheet 1 62am [/A zau.

INVENTOR 2 Sheets-Sheet 2 life ,lld Zc I l I FIG. /3.

620/; flA/A/VZfZL INVENTOR c. J. YLINZELL COLLETS AND OTHER WORKHOLDERS Dec. 13,1960

Filed Jan. 11, 1960 I l-lllll United States PatentO 2364,32; COLLETS AND: OTHER woR-KHoLnE-Rs v CecilJohn Linzell; Witney,- England; assignor to C i-aw-;

ford Collets Limited,@ Witney, England, a company of Great Britain This invemihn relates to colletsandother' work-holder's, and in particular tocollets' provided with'detachable' worle engaging'pads V H n v One object' of the" present invention is to provide a work-holder siich as a" collet having oneorf more workengaging pad's each of whiclris readily releasable front the work-holder, the means for locking the pad to the "jaw aud tor releasing the paid from the jaw'beings'imple to manufacture and to-operate' and involving the minimum of moving parts. v n l The" invention provides a work-holder comprising in combination a jawpa work-engaging pad; means for progressively urgin'g'said paid into engagement with said jaw; said means comprising aspring', a member supportedby said jaw for movement longitudinally thereof =uriderthe force of said spring, said member having a su'rface'facing said. jaw and inclined ito the direction of movement of the member; which surface'isi ad'aptedtoengage-against a cooperating surface on said pad,'s'aid co -operating surface facing. away from saidf jaw and lyingisubstantially parallel to said surfacei onjsaidfmeinber. a p r g The invention further pr'o'vides a work-holder comprising" in 'combination'a' jaw, ar work-engaging pad, means for locating said pad on, said jaw, means for releasably locking said pad to said jaw, said means c'ompri'singa plunger slida'ble in a re-e'nt'r'ant keyway' extending parallel to the lengthof thejaW'fornTed Hn one meiiiber of the pair of members consisting of saidpad and said jaw, mutually en agi g member's com rising adovetailmember and meansdefining'ja dovetail sl'ot adapted to receive said dovetail member, one, of said engaging members forming part of said" plunger a'ndthe otlier jof said en aging members" forming part of the other member of said pair of members, the mutuallyengag'in'g surfacesof said dovetail member fand slot lying fat: an inclination to'tlie direction at movement of the plunger? 7 I oneembodiment of tlie invention is shown, by: way ofexamplefonlyg inthe' accom anying drawing in-which Figure 1 is a section through aj c'ollet'j Figure- 2 is-a plan viewof the; collet of Figure l;

, Figure ?Jisa-rear-Viw o'f a work-engagingpad-witli-a plunger and spring attached theretoi- Figure 4 is -a perspective view of -tlie Work-engaging pad;

Figure Sis-a"perspectiveview o'fthe lunger-and sprin g;

Figures 6 and 7 are respectively a plan view frorn below and a side view .of the plunger;.

Figures8and '9 are section's"throughpart of the collet showing the positions-=of1-theplungenin which the work- Figure, 11- is an elevation o f tlie work-engagrng-llpad seen from the rear;

Figures 12 and 13 are views from below of the workengaging pad with the plunger respectively in position and removed.

Patented Dec. 13, 1960 slits 10a to provide a number of similar jaws 10b, for

example three, and on the inside of each" jaw a workengaging pad Ills-supported. As the three" work-engag injg pads and'their means of support will usually be identical, only onewill be described.

Around the outerface of thepad, a shoulder lla is formed the sides of the shoulder lyingin planes normal to the longitudinal axislof the when A corresponding groove 10b is formed in the inner face of thecollet jaw, against which face the pad abuts, to receivethe shoulder and thereby prevent movement of the pad in a'dir'ection parallel to the'lon'gitudinal axis of the collet.

The pad is held in position onthejaw by means which permit it to be readily released when desired; These means compriseaplunger 12 which fits slidingly in a chamber 10d (Figures 1 and 8) formed longitudinally in the jaw in a mid-position and opening along its length throughtthe concave surface of thejaw in-the manner of a re-entrant; slot. This isbest seen in Figure-1 where the plunger is in position but the-pad hasbeen removed.

a The plunger-12,. which over a short upper portion 12a is of circular :eross-sectiomis' part cylindricalbelow this upper portion and has a substantially flat face 12b parallel to the axisof the plunger over a mid-portion; over a lower portionwit is formed with a dovetai-l'shaped-key 120, the outer surface 12dof the dovetail, that is the surface between the inclined sides thereof} lying at a small acute angle,.for example 7 to the flat face of the mid-portion ofthe' plungentthez-faces l2e of the plunger oneitherside of the base of the dovetailbeingparallelto the outer surface 12d of the dovetailr The' shoulder 11a 'on: the pad inthe-vicinity of the plnngerris cut' away to provide a dovetail keyway- 1-1-b matchingthe dovetail key- 120- of-the plungerin shape and inclination, the face of the shoulderwhich lies'adjacent the baseof the groove 10a in the jaw beingchamfered on either side of the dovetail keyway to match the-inclined faces'lza of the plunger on 'either side-of the dovetail key.

It a will be evidenttherefore-that if the-pad is fitted in place when the plunger is. in-- alow position in its-cham'- her," on raising the plunger the dovetaii'key willenter the dovetail keyway in the padand the inclination of the engagingsurfaces will pull the-pad into progressively tighter cont-actwith the jaw.-

The movementof' the plunger is manually controlled against the force of a spring-13* which at-its upper end fits intoa cupped recess-s 12g in thebaseof the "plunger and at its lower end'engages thebaseof the chamber.

Since the upper end 1 of the-plunger is fully circular, an

adjacent part of the pad 11 is cut away at 11d toallow free movement of the plungerupwardstand downwards, and thelength ofthe cutaway portiondet'erminesthe lower limit-ofmovementof the-plunger; V The upward movement; of-tlie plunger is limited by a stop; in theform of a screw 14 whichis screwed into the end face ofethe-"jaw untilthe-'headlies flush with the face of the jaw, but protrudes laterally into the charliber and'engag'es-in-a shortarcuate slot- 12h-in the side of the-plunger: 'The plunger may of coursebe -removed-by firstremoving this-screw.- The-screw head 'also serves to prevent-rotationof? the-plunger within the chamber.

Imoperationof this-device; on depressing the plunger 12 against'theforce of the-spring 13; the dovetail key llciofthe'plunger; is -slidout" of -thedovetail keyway' of pad and, by the inclination of the engaging surfaces, lock:

locking position, the device cannot easily be mishandled.

as for example may be a device employing screw-threaded locking arrangements which may be damaged through overtightening or alternatively work loose through undertightening. It will also be appreciated that by means of this form of locking and release arrangement, a very rapid change of the work-engaging pads may be effected.

Whilst most of the parts described above may be produced by conventional machine-shop methods, it may be preferable to form the plunger by a sintering method.

In a modification of the above embodiment the dovetail key may be provided on the pad, instead of on the plunger, in which case the dovetail keyway will be provided in the plunger.

The above embodiments may also be modified by arranging for the plunger to be raised or lowered on a screw-threaded rod which is rotatable by a key or screwdriver fitted into a head on the rod located in the end face of the jaw.

According to a further modification, the pad may engage with the jaw through a shoulder provided on the jaw to fit into a corresponding recess in the pad.

It will be evident that whilst a dovetail key and keyway have been described above for providing the wedge action by which the pads are held tightly to the jaws, alternative devices providing a similar wedge effect may be designed within the scope of the invention.

I claim:

1. A work-holder comprising in combination a jaw, a work-engaging pad, means for progressively urging said pad into engagement with said jaw, said means comprising a spring, a member supported by said jaw for movement longitudinally thereof under the force of said spring, said member having a surface facing said jaw and inclined to the direction of movement of the member, which surface is adapted to engage against a co-operating surface on said pad, said co-operating surface facing away from said jaw and lying substantially parallel to said surface on said member.

2. A work-holder comprising in combination a jaw, a work-engaging pad, means for locking said work-engaging pad on said jaw, said means comprising a wedge member movable longitudinally of the work-holder to progressively urge said pad into abutment with said jaw.

3. A work-holder comprising in combination a jaw, a work-engaging pad, means for locating said pad on said jaw, means for releasably locking said pad to said jaw, said means comprising a plunger slidable in a re-entrant keyway in one of the pair of members formed by said pad and said jaw, a shoulder formed on said plunger, a shoulder formed on the other member of said pair, one of said shoulders having a surface elongated at an inclination to the direction of movement of the plunger and facing towards the member on which said shoulder is formed, the other shoulder being adapted to engage slidingly against said surface and spring'means for urging said shoulders into progressively tighter mutual engagement to lock said pad to said jaw, said plunger being movable against the force of said spring means to release said pad from said jaw.

4. A work-holder comprising in combination a jaw, a work-engaging pad, said pad forming with said jaw a pair of interengaging members, at least one projection from one of said interengaging members abutting against a co-operating recess in the other of said members to prevent movement of the pad in at least one direction along the jaw, and means movable alternatively to release said pad from said jaw and to progressively urge said pad into engagement with said jaw, said means comprising a plunger slidable in a re-entrant keyway extending longitudinally within said jaw, a dovetail projection on said plunger, said pad having a dovetail recess adaptedto receive said dovetail projection, those surfaces of said dovetail projection which abut co-operating surfaces of the recess being inclined to the direction of movement of the plunger and a spring adapted to urge said plunger in a direction in which the dovetail projection enters said recess and progressively presses the pad towards the jaw and in which said projection is pressed against a face of said co-operating recess.

5. A work-holder comprising in combination a jaw, a work-engaging pad, said pad forming with said jaw a pair of interengagingmembcrs, at least one projection from one of said interengaging members adapted to engage against a face of a recess in the other of said members to prevent movement of the pad in at least one direction along the jaw, movable locking means slidably mounted on one of said interengaging members, the other of said interengaging members having fixed locking means, a spring adapted to urge said fixed and movable locking means into mutual engagement to lock said pad to said aw.

6. A collet having a plurality of longitudinal slots defining a plurality of collet jaws, a plurality of work engaging pads, each pad forming with a jaw a pair of interengaging members, at least one shoulder projecting from one of said members adapted to engage in a corresponding recess in the other of said members to prevent movement of the pad in at least one direction along the jaw, said jaw having a re-entrant slot in a face thereof adjacent the pad, a plunger slidably mounted in said slot, a spring urging said plunger towards the outer end of said jaw, a dovetail key formed on said plunger, a dovetail keyway formed in said pad to receive said dovetail key, the interengaging surface of said key and keyway being inclined to the direction of movement of the plunger to cause the plunger when moving under the force of the spring to pull said pad into progressively tighter engagement with the jaw.

7. A collet comprising a plurality of spring-loaded plungers and a plurality of work-engaging pads. each of said pads being interlocked with a respective one of said plungers in a predetermined position of said pad into which the pad is urged by its spring loading, each pad being released from the collet by movement of its interlocking plunger away from said predetermined position.

8. A collet comprising a plurality of work-engaging pads, a plurality of plungers, said plungers being equal in number to said pads, said collet having an axial bore which is recessed at spaced intervals to accommodate said plungers, a plurality of resilient means, each plunger being engaged by one of said resilient means and normally being urged thereby into a predetermined position relative to said bore, each pad having a portion thereof interlocking with a portion of a respective plunger, interengaging surfaces of said pad portion and said plunger portion being inclined at an angle to the axis of said axial collet bore whereby movement of said plunger into said predetermined position draws said pad towards said plunger.

References Cited in the file of this patent UNITED STATES PATENTS 1,457,307 Kerns June 5, 1923 1,924,301 Benford Aug. 29, 1933 2,234,603 OConnell Mar. 11, 1941 2,382,060 Ingalls Aug. 14, 1945 2,580,067 Barnes Dec. 25, 1951 

